Mobile telephones, tablet terminals, and Personal Digital Assistants (PDAs) have been widely used as mobile terminal devices, in which much ingenuity has been exercised in the arrangement of receivers, speakers and the like. In a mobile terminal device disclosed in each of Patent literature 1 and 2, a receiver sound hole is formed in an upper part of a principal surface of a housing and a speaker sound hole is formed on a side surface arranged in the lateral direction of the housing.